Skeletal Muscle Anatomy and Function Quiz
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Questions and Answers

What is the primary function of the phosphagen system?

  • To break down glucose into pyruvate
  • To provide immediate ATP using creatine phosphate (correct)
  • To convert fatty acids into energy
  • To utilize oxygen for energy production

    • Which of the following correctly describes the duration of ATP production via the phosphagen system?

  • Up to 30 seconds of sustained energy
  • Only for aerobic exercise lasting more than 5 minutes
  • Continuous energy supply lasting over 5 minutes
  • A maximum of 3-15 seconds of immediate energy (correct)

    • What type of exercise primarily utilizes the anaerobic glycolysis system?

  • Low-impact aerobic exercises focusing on endurance
  • Long-distance running with high oxygen demand
  • High-intensity, short-duration power activities (correct)
  • Continuous moderate lifting with low rest

    • Which substrate is converted into pyruvate during glycolysis?

    <p>Glucose</p> Signup and view all the answers

    Which statement about oxygen usage in energy systems is true?

    <p>Anaerobic glycolysis can function without oxygen</p> Signup and view all the answers

    What is the primary function of the actin filament in a sarcomere?

    <p>Sliding over myosin during contraction</p> Signup and view all the answers

    What is the role of troponin in muscle contraction?

    <p>Regulating the interaction between actin and myosin</p> Signup and view all the answers

    During which phase is a muscle the strongest?

    <p>In the middle of its range of motion</p> Signup and view all the answers

    Which statement correctly describes the mechanism of an eccentric contraction?

    <p>Involves slow relaxation of myosin heads</p> Signup and view all the answers

    What is the significance of the Z band in a sarcomere?

    <p>It defines the boundaries of the sarcomere</p> Signup and view all the answers

    How many actin filaments surround each myosin filament in a sarcomere?

    <p>6 actin filaments</p> Signup and view all the answers

    What role does titin play in the muscle fiber?

    <p>Providing resistance and elasticity to stretch</p> Signup and view all the answers

    What structural component is known as a fascicle in skeletal muscle?

    <p>A bundle of muscle fibers</p> Signup and view all the answers

    What state are the Na+ gates in during the resting membrane potential?

    <p>Closed</p> Signup and view all the answers

    What initiates an action potential after a stimulus is received?

    <p>Dendrites or soma</p> Signup and view all the answers

    During the depolarization phase, what is the state of the K+ gates?

    <p>Closed</p> Signup and view all the answers

    What happens to the Na+ gates during the repolarization phase?

    <p>They are inactivated</p> Signup and view all the answers

    What ion movement occurs during hyperpolarization?

    <p>K+ out</p> Signup and view all the answers

    What principle outlines that an action potential can only occur at a certain amplitude?

    <p>All or none principle</p> Signup and view all the answers

    What is the function of the absolute refractory period during repolarization?

    <p>To prevent backwards propagation of action potentials</p> Signup and view all the answers

    What describes the structural nature of myelin?

    <p>Lipid</p> Signup and view all the answers

    What phase of muscle contraction is represented when a weight is raised during a bench press?

    <p>Concentric phase</p> Signup and view all the answers

    Where are the cell bodies of alpha motor neurons located in the body?

    <p>In the spinal cord</p> Signup and view all the answers

    Which neurotransmitter is primarily responsible for synaptic transmission at the neuromuscular junction?

    <p>Acetylcholine</p> Signup and view all the answers

    What is the term for the maximum amount of weight that can be raised in a concentric phase?

    <p>One-repetition maximum</p> Signup and view all the answers

    What is the role of action potentials in muscle contraction?

    <p>They facilitate communication between the brain and muscles.</p> Signup and view all the answers

    Which contraction phase occurs when a weight is being lowered during a bench press?

    <p>Eccentric phase</p> Signup and view all the answers

    What physiological process occurs when neurotransmitters bind to the muscle cell membrane?

    <p>Calcium ion release from the sarcoplasmic reticulum</p> Signup and view all the answers

    What does a 1-repetition maximum test primarily measure?

    <p>Maximal strength output</p> Signup and view all the answers

    Which of the following correctly describes the P-R interval in the cardiac cycle?

    <p>The time it takes for electrical activity to travel from the atria to the ventricles.</p> Signup and view all the answers

    In Wigger’s Diagram, what does the aortic valve closing signify?

    <p>The end of ventricular filling.</p> Signup and view all the answers

    Which cardiac arrhythmia is characterized by an irregular, often rapid heart rate due to chaotic electrical signals in the atria?

    <p>Atrial Fibrillation</p> Signup and view all the answers

    What is the electrical event represented by the QRS complex in an electrocardiogram?

    <p>Ventricular depolarization</p> Signup and view all the answers

    What is the term for a heart rate that is faster than normal, opposite to bradycardia?

    <p>Tachycardia</p> Signup and view all the answers

    What is the total number of ATP produced from 10 NADH molecules during cellular respiration?

    <p>25 ATP</p> Signup and view all the answers

    How many NADH are produced from one complete turn of the Krebs cycle?

    <p>3 NADH</p> Signup and view all the answers

    What is the correct stoichiometry for the creation of water in the electron transport chain?

    <p>2H + ½ O + 2e- → H2O</p> Signup and view all the answers

    From pyruvate to acetyl Co-A, how many NADH molecules are generated?

    <p>2 NADH</p> Signup and view all the answers

    How many turns of the Krebs cycle occur for each molecule of glucose metabolized?

    <p>2 turns</p> Signup and view all the answers

    How much ATP is produced from one FADH2 during the electron transport chain?

    <p>1.5 ATP</p> Signup and view all the answers

    Which hormone is primarily responsible for regulating blood glucose levels?

    <p>Glucagon</p> Signup and view all the answers

    What is the actual total ATP production for one glucose molecule after glycolysis, the Krebs cycle, and the electron transport chain?

    <p>32 ATP</p> Signup and view all the answers

    What is the primary function of catecholamines?

    <p>Promoting stress response</p> Signup and view all the answers

    During glycolysis, how many ATP are used initially to convert glucose to pyruvate?

    <p>2 ATP</p> Signup and view all the answers

    Which pair of hormones is involved in the regulation of stress and metabolism?

    <p>Epinephrine and norepinephrine</p> Signup and view all the answers

    Which hormone primarily contributes to the development of male secondary sexual characteristics?

    <p>Testosterone</p> Signup and view all the answers

    Which hormone is secreted in response to low blood glucose levels?

    <p>Glucagon</p> Signup and view all the answers

    What is the primary role of growth hormone in the body?

    <p>Promoting muscle growth and development</p> Signup and view all the answers

    Which hormone is primarily involved in maintaining fluid balance in the body?

    <p>Aldosterone</p> Signup and view all the answers

    Which of the following is a primary function of epinephrine?

    <p>Preparing the body for 'fight or flight'</p> Signup and view all the answers

    Which of these hormones plays a role in both metabolism and the stress response?

    <p>Cortisol</p> Signup and view all the answers

    Which pair of hormones is commonly associated with the body's response to stress?

    <p>Epinephrine and norepinephrine</p> Signup and view all the answers

    What hormone is primarily responsible for increased sodium reabsorption and water retention during exercise?

    <p>Aldosterone</p> Signup and view all the answers

    Which physiological response occurs when blood volume decreases due to fluid loss from exercise?

    <p>Increased Renin release</p> Signup and view all the answers

    What is the effect of angiotensin II following blood volume loss?

    <p>Increased aldosterone release</p> Signup and view all the answers

    Under what condition is erythropoietin released from the kidneys?

    <p>Hypoxia</p> Signup and view all the answers

    What is the primary effect of aldosterone on kidney function?

    <p>Increases potassium excretion</p> Signup and view all the answers

    How does exercise influence blood pressure via hormonal responses?

    <p>Increased production of angiotensin II</p> Signup and view all the answers

    Which of the following mechanisms contributes to increased heart rate during exercise?

    <p>Increased sympathetic nervous system activity</p> Signup and view all the answers

    What immediate effect does prolonged exercise have on blood composition?

    <p>Increased blood concentration</p> Signup and view all the answers

    What does increased ADH release primarily promote in response to exercise?

    <p>Increased water absorption</p> Signup and view all the answers

    Which of the following statements about the effects of exercise on the cardiovascular system is true?

    <p>Exercise enhances the release of aldosterone.</p> Signup and view all the answers

    What causes air to leave the lungs during expiration?

    <p>Reduction in lung volume</p> Signup and view all the answers

    What is the relationship between lung pressure and lung volume during expiration?

    <p>Lung pressure increases while lung volume decreases</p> Signup and view all the answers

    How does pressure in the pleural space relate to lung pressure during a typical breath cycle?

    <p>Pleural space pressure decreases as lung volume increases</p> Signup and view all the answers

    What occurs at the end of expiration in terms of pressure and lung volume?

    <p>Lung volume is decreasing while pressure equalizes to 760 mmHg</p> Signup and view all the answers

    What effect does diaphragm relaxation have on lung dynamics during expiration?

    <p>It leads to a decrease in lung volume and an increase in lung pressure</p> Signup and view all the answers

    Which structure is responsible for the delivery of deoxygenated blood from the body back to the heart?

    <p>Inferior vena cava</p> Signup and view all the answers

    What is the correct pathway of blood flow starting from the lungs?

    <p>Lungs → left atrium → left ventricle → aorta → arteries</p> Signup and view all the answers

    What does an electrocardiogram (ECG) primarily measure?

    <p>Electrical activity of the heart</p> Signup and view all the answers

    Which heart valve separates the left atrium from the left ventricle?

    <p>Bicuspid (mitral) valve</p> Signup and view all the answers

    Which component is NOT part of the cardiovascular pathway of blood?

    <p>Neurons</p> Signup and view all the answers

    Which of the following structures includes the valves that prevent backflow of blood in the heart?

    <p>Chambers of the heart</p> Signup and view all the answers

    What is the function of pulmonary arteries in the circulatory system?

    <p>Carry deoxygenated blood to the lungs</p> Signup and view all the answers

    What does the QRS complex in an ECG represent?

    <p>Ventricular depolarization</p> Signup and view all the answers

    Which of the following best describes the role of the aortic valve?

    <p>Allows oxygenated blood to flow into the aorta</p> Signup and view all the answers

    Where is the electrical activity recorded in an electrocardiogram generated?

    <p>Sinoatrial node</p> Signup and view all the answers

    How many total NADH molecules are produced during one complete turn of the Krebs cycle?

    <p>6 NADH</p> Signup and view all the answers

    What role does oxygen play in the electron transport chain?

    <p>It serves as the final electron acceptor</p> Signup and view all the answers

    Which hormone increases in response to decreased insulin levels during exercise?

    <p>Catecholamines</p> Signup and view all the answers

    Which component is responsible for ATP synthesis in the mitochondria during the electron transport chain?

    <p>ATP synthase</p> Signup and view all the answers

    During which phase of muscle contraction is motor unit recruitment primarily controlled?

    <p>Concentric phase</p> Signup and view all the answers

    What is the effect of an increase in aortic pressure on stroke volume?

    <p>Decreases stroke volume</p> Signup and view all the answers

    Which muscles are primarily involved in active exhalation during vigorous exercise?

    <p>Internal intercostals and abdominals</p> Signup and view all the answers

    How is water formed during the electron transport chain process?

    <p>From electrons, protons, and oxygen</p> Signup and view all the answers

    What stimulates the release of glucagon during exercise?

    <p>Low blood glucose levels</p> Signup and view all the answers

    Which part of the heart receives deoxygenated blood from the body?

    <p>Right atrium</p> Signup and view all the answers

    What initiates the release of acetylcholine (ACh) at the neuromuscular junction?

    <p>Action potential reaching the axon terminal</p> Signup and view all the answers

    What role does calcium play in skeletal muscle contraction?

    <p>It binds to troponin, exposing binding sites on actin</p> Signup and view all the answers

    How is aldosterone stimulated in relation to the renin-angiotensin-aldosterone system (RAA)?

    <p>Through the release of renin from juxtaglomerular cells</p> Signup and view all the answers

    What occurs during the repolarization phase of an action potential in skeletal muscle cells?

    <p>Potassium ions exit the cell, restoring resting membrane potential</p> Signup and view all the answers

    Which ion flow is primarily responsible for the depolarization phase of the action potential in motor neurons?

    <p>Sodium influx</p> Signup and view all the answers

    In muscle contraction, what occurs after the neuromuscular signal ends?

    <p>Calcium is pumped back into the sarcoplasmic reticulum</p> Signup and view all the answers

    Which hormone is released by the posterior pituitary in response to increased plasma osmolarity?

    <p>Antidiuretic hormone (ADH)</p> Signup and view all the answers

    What is the end result of repeated cross-bridge cycling during muscle contraction?

    <p>Shortening of the muscle fiber leading to contraction</p> Signup and view all the answers

    What initiates the action potential at the axon hillock of a motor neuron?

    <p>Depolarization of the dendrites</p> Signup and view all the answers

    During skeletal muscle contraction, what role does calcium play?

    <p>It uncovers binding sites on actin filaments</p> Signup and view all the answers

    What is the consequence of decreased renal perfusion pressure on the RAA system?

    <p>Increased renin release</p> Signup and view all the answers

    What happens to potassium ions during repolarization of the action potential?

    <p>They exit the cell</p> Signup and view all the answers

    Which hormone is released by the posterior pituitary gland in response to increased plasma osmolarity?

    <p>Antidiuretic hormone (ADH)</p> Signup and view all the answers

    What effect does angiotensin II have on the kidneys?

    <p>Stimulates aldosterone release</p> Signup and view all the answers

    In skeletal muscle contraction, what occurs after the nerve signal ceases?

    <p>Calcium is pumped back into storage</p> Signup and view all the answers

    What is the net ATP yield from glycolysis before entering the Krebs cycle?

    <p>2 ATP</p> Signup and view all the answers

    What is the role of NADH and FADH2 in the electron transport chain?

    <p>They donate electrons to the transport chain.</p> Signup and view all the answers

    Which hormone increases during exercise to help control blood glucose levels?

    <p>Glucagon</p> Signup and view all the answers

    How does the electron transport chain utilize hydrogen ions (H+)?

    <p>They create a proton gradient to drive ATP synthesis.</p> Signup and view all the answers

    What physiological effect does increased aortic pressure have on the heart?

    <p>It decreases overall stroke volume.</p> Signup and view all the answers

    What is the primary function of ATP synthase in the electron transport chain?

    <p>To produce ATP from ADP and inorganic phosphate.</p> Signup and view all the answers

    During inhalation, which muscles are primarily involved?

    <p>Sternocleidomastoid and diaphragm.</p> Signup and view all the answers

    What is the consequence of asynchronous motor unit recruitment?

    <p>It allows for sustained contractions without fatigue.</p> Signup and view all the answers

    How many ATP are produced from one FADH2 during the electron transport chain?

    <p>1.5 ATP</p> Signup and view all the answers

    What is the correct sequence of blood flow through the heart?

    <p>Right atrium, right ventricle, lungs, left atrium, left ventricle, aorta</p> Signup and view all the answers

    Study Notes

    Skeletal Muscle Anatomy and Function

    • Skeletal muscle consists of fascicles, also known as bundles of muscle fibers (cells).
    • Key components of muscle fiber: myofibrils and sarcomeres, which are the basic contractile units.
    • Sarcomeres contain actin and myosin filaments, responsible for muscle contraction.
    • The Z band defines the boundaries of each sarcomere.

    Sarcomere Function

    • Actin filaments slide during muscle contraction, aided by the mechanism of muscle proteins.
    • Eccentric contractions involve slow relaxation of myosin heads and stretching of connective tissue forces.
    • Each myosin has several actin filaments surrounding it, which enhances the interaction during contraction.

    Muscle Strength Dynamics

    • Muscles exhibit maximum strength in mid-range positions during contractions.
    • Muscles are weakest when at extreme positions with no overlap of actin and myosin.

    Range of Motion in Muscle Contraction

    • Different phases of contraction include concentric (muscle shortening), isometric (muscle length stays constant), and eccentric (muscle lengthening).
    • A 1-repetition maximum is defined as the heaviest weight that can be lifted in a single effort through a full range of motion.

    Alpha Motor Neurons

    • Cell bodies of motor neurons are located in the spinal cord.
    • Action potentials facilitate communication between the brain and muscles, traveling along axons.

    Synaptic Transmission

    • Acetylcholine (Ach) is the neurotransmitter at the neuromuscular junction (NMJ).
    • Binding of Ach to muscle membrane triggers depolarization, beginning an action potential in the muscle cell.

    Action Potential Phases

    • Resting Membrane Potential: Sodium (Na+) gates are closed; potassium (K+) gates also remain closed.
    • Depolarization: Na+ gates open, allowing Na+ to flow into cells.
    • Repolarization: Na+ gates inactivate, K+ gates open, allowing K+ to exit cells.
    • Hyperpolarization: Na+ gates remain inactive; K+ gates open; ion movement stops after initial outflow.

    All or None Principle

    • The action potential exhibits an all-or-none response, with amplitude remaining constant.
    • Variation in stimulus strength is achieved through the frequency of action potentials.

    Energy Transfer Systems

    • Three main energy systems:
      • ATP-CP System: Provides immediate ATP via creatine phosphate, lasting 3-15 seconds without oxygen.
      • Glycolysis: Converts glucose to pyruvate, playing a crucial role in both anaerobic and aerobic energy production.

    Cardiac Physiology

    • Wigger’s Diagram depicts cardiac cycle events including atrial depolarization (P wave) and ventricular depolarization (QRS complex).
    • Cardiac arrhythmias can manifest as bradycardia, atrial fibrillation, ventricular tachycardia, and ventricular fibrillation.
    • Bradycardia refers to abnormally slow heart rate, while tachycardia denotes an excessively fast pulse.

    Practical Example: Exercise Dynamics

    • Bench press showcases concentric, isometric, and eccentric contractions in a full range of motion.

    Cellular Respiration Overview

    • NAD+ is reduced to NADH during metabolic processes.
    • Water is formed at the end of the Electron Transport Chain (ETC) through the reaction 2H + ½ O + 2e- → H2O.

    Glycolysis

    • Converts glucose to pyruvate.
    • ATP consumption: 2 ATP.
    • ATP production: 4 ATP (net gain: 2 ATP).
    • NADH produced: 2 NADH.

    Pyruvate to Acetyl CoA

    • Produces 2 NADH.

    Krebs Cycle (Citric Acid Cycle)

    • Each cycle produces:
      • 3 NADH
      • 1 FADH2
      • 1 ATP
    • Each glucose undergoes 2 turns of the Krebs Cycle.

    Electron Transport Chain Efficiency

    • Each NADH yields approximately 2.5 ATP.
    • Each FADH2 yields approximately 1.5 ATP.

    Total ATP Production Calculation

    • From 10 NADH: 2.5 x 10 = 25 ATP.
    • From glycolysis: 2 ATP.
    • From Pyruvate to Acetyl CoA: 2 NADH = 2 ATP.
    • From Krebs cycle: 6 NADH = 15 ATP; 2 FADH2 = 3 ATP; total from Krebs cycle = 20 ATP.
    • Overall, total ATP = 32 ATP.

    Metabolism of Fat and Protein

    • Enhanced water absorption and blood pressure during metabolism alters renal function.
    • Increases Na+ reabsorption, causing potassium excretion, elevated heart rate, sympathetic nervous system activity, and aldosterone levels.

    Water Retention Mechanism

    • Exercise-induced fluid loss concentrates blood, reducing blood volume.
    • Response includes:
      • Increased ADH and renin release, leading to angiotensin II production.
      • Angiotensin II causes vasoconstriction and increases aldosterone and ADH release, aiding water retention.

    Erythropoietin Function

    • Released from kidneys in response to low red blood cell count or hypoxia.
    • Stimulates the production of red blood cells.

    Catecholamines Role

    • Involve neurotransmitters like epinephrine and norepinephrine, affecting various physiological responses.

    Heart Anatomy and Blood Flow Pathway

    • Know the chambers and valves of the heart.
    • Blood flow pathway: Lungs → left atrium → left ventricle → aorta → arteries → arterioles → capillaries → venules → veins → vena cava → right atrium → right ventricle → lungs.

    Electrocardiograph (ECG or EKG)

    • Measures electrical activity of the heart.
    • Records changes reflecting heart rhythm and potential abnormalities.

    Respiratory Mechanics

    • During expiration, pleural pressure changes inducing air to leave the lungs.
    • Pressure in the pleural space decreases while lung volume increases and intrapleural pressure rises.

    Summary of Pressure Changes

    • At rest, pleural pressure and lung volume are balanced at 760 mmHg.

    Skeletal Muscle Contraction Process

    • Initiation: Brain sends signals down motor neurons to stimulate movement.
    • Action Potential Generation: Stimulus received at dendrites of motor neuron in the spinal cord triggers an action potential at the axon hillock.
    • Neuromuscular Junction (NMJ): Arrival of action potential at the axon terminal releases acetylcholine (ACh).
    • Ion Exchange: ACh binds to receptors on the muscle cell, causing sodium (Na+) influx, leading to depolarization.
    • Action Potential Phases:
      • Depolarization: Rapid Na+ influx through open channels.
      • Repolarization: K+ efflux through channels as Na+ channels close.
      • Hyperpolarization: Brief phase of increased negativity occurs following repolarization.
    • Absolute Refractory Period: Sodium channels have two gates; one opens for depolarization and the other closes, preventing another action potential.
    • Calcium Release: Depolarization triggers calcium release from the sarcoplasmic reticulum, which binds to troponin, exposing binding sites on actin.
    • Cross-Bridge Cycling: Myosin heads attach to actin filaments, causing contraction by pulling actin inward.
    • Relaxation: When signals stop, calcium is pumped back into storage, leading to muscle relaxation.

    Hormones Maintaining Fluid and Electrolyte Balance During Exercise

    • Renin: Released by juxtaglomerular cells in response to decreased renal perfusion pressure; stimulates RAA system.
    • ADH (Vasopressin): Released by the posterior pituitary gland due to increased plasma osmolarity and decreased blood volume; promotes water retention.
    • Angiotensin II: Triggered by renin release, it promotes aldosterone secretion and increases blood pressure.
    • Aldosterone: Released from adrenal cortex upon RAA activation; enhances sodium reabsorption, potassium excretion, and water retention.
    • RAA System: Decreased blood pressure leads kidneys to release renin, converting angiotensinogen to angiotensin I, which is then converted to angiotensin II by ACE.

    Hormones Controlling Blood Glucose During Exercise

    • Insulin: Levels decrease, inhibiting glucose uptake into cells.
    • Glucagon: Released from the pancreas to raise blood glucose levels.
    • Epinephrine and Norepinephrine: Released by adrenal medulla, increasing glucose availability.
    • Cortisol: Released from adrenal cortex to facilitate gluconeogenesis and fat metabolism.
    • Growth Hormone: Levels rise to mobilize fat stores and influence protein metabolism.

    Electron Transport Chain (ETC) Function

    • Electron Donation: NADH and FADH2 transfer electrons to the ETC, creating a proton (H+) gradient.
    • ATP Production: ATP synthase utilizes the proton gradient to convert ADP and inorganic phosphate into ATP.
    • Water Formation: Oxygen serves as the final electron acceptor, combining with electrons and protons to form water.
    • Energy Yield:
      • NADH results in approximately 2.5 ATP.
      • FADH2 results in approximately 1.5 ATP.

    Muscle Force Generation

    • Motor Unit Recruitment: Small or large numbers of motor units activated to control force output.
    • Action Potential Frequency: Determines the type of muscle contraction; higher frequency leads to stronger contractions.
    • Asynchronous Recruitment: Different motor units activate at different times to maintain sustained force without fatigue.

    Heart Anatomy and Function

    • Pathway of Blood:
      • Blood enters the right atrium via the superior vena cava.
      • Flows through the tricuspid valve to the right ventricle.
      • Exits through the pulmonary valve into the pulmonary trunk and lungs.
      • Returns via pulmonary veins to the left atrium.
      • Moves through the bicuspid (mitral) valve into the left ventricle.
      • Finally, exits through the aortic valve into the aorta.
    • ECG Waves:
      • P-Wave: Atrial depolarization initiating contraction.
      • QRS Complex: Ventricular depolarization, leading to ventricular contraction.
      • T-Wave: Ventricular repolarization, allowing for recovery.
    • AV and Aortic Valve Function: AV valves open and close based on pressure differences; increased aortic pressure impacts afterload and stroke volume.

    Breathing Mechanism

    • Inhalation:
      • Active process involving diaphragm, sternocleidomastoid, and intercostal muscles.
      • Volume increases, pressure decreases in the thoracic cavity.
    • Exhalation:
      • Can be passive or active; muscles include internal intercostals and abdominal muscles.
      • Volume decreases, pressure increases.
    • Pathway of Changes: Changes in pleural and lung spaces drive airflow during breathing.

    Skeletal Muscle Contraction Process

    • Initiation: Brain sends signals down motor neurons to stimulate movement.
    • Action Potential Generation: Stimulus received at dendrites of motor neuron in the spinal cord triggers an action potential at the axon hillock.
    • Neuromuscular Junction (NMJ): Arrival of action potential at the axon terminal releases acetylcholine (ACh).
    • Ion Exchange: ACh binds to receptors on the muscle cell, causing sodium (Na+) influx, leading to depolarization.
    • Action Potential Phases:
      • Depolarization: Rapid Na+ influx through open channels.
      • Repolarization: K+ efflux through channels as Na+ channels close.
      • Hyperpolarization: Brief phase of increased negativity occurs following repolarization.
    • Absolute Refractory Period: Sodium channels have two gates; one opens for depolarization and the other closes, preventing another action potential.
    • Calcium Release: Depolarization triggers calcium release from the sarcoplasmic reticulum, which binds to troponin, exposing binding sites on actin.
    • Cross-Bridge Cycling: Myosin heads attach to actin filaments, causing contraction by pulling actin inward.
    • Relaxation: When signals stop, calcium is pumped back into storage, leading to muscle relaxation.

    Hormones Maintaining Fluid and Electrolyte Balance During Exercise

    • Renin: Released by juxtaglomerular cells in response to decreased renal perfusion pressure; stimulates RAA system.
    • ADH (Vasopressin): Released by the posterior pituitary gland due to increased plasma osmolarity and decreased blood volume; promotes water retention.
    • Angiotensin II: Triggered by renin release, it promotes aldosterone secretion and increases blood pressure.
    • Aldosterone: Released from adrenal cortex upon RAA activation; enhances sodium reabsorption, potassium excretion, and water retention.
    • RAA System: Decreased blood pressure leads kidneys to release renin, converting angiotensinogen to angiotensin I, which is then converted to angiotensin II by ACE.

    Hormones Controlling Blood Glucose During Exercise

    • Insulin: Levels decrease, inhibiting glucose uptake into cells.
    • Glucagon: Released from the pancreas to raise blood glucose levels.
    • Epinephrine and Norepinephrine: Released by adrenal medulla, increasing glucose availability.
    • Cortisol: Released from adrenal cortex to facilitate gluconeogenesis and fat metabolism.
    • Growth Hormone: Levels rise to mobilize fat stores and influence protein metabolism.

    Electron Transport Chain (ETC) Function

    • Electron Donation: NADH and FADH2 transfer electrons to the ETC, creating a proton (H+) gradient.
    • ATP Production: ATP synthase utilizes the proton gradient to convert ADP and inorganic phosphate into ATP.
    • Water Formation: Oxygen serves as the final electron acceptor, combining with electrons and protons to form water.
    • Energy Yield:
      • NADH results in approximately 2.5 ATP.
      • FADH2 results in approximately 1.5 ATP.

    Muscle Force Generation

    • Motor Unit Recruitment: Small or large numbers of motor units activated to control force output.
    • Action Potential Frequency: Determines the type of muscle contraction; higher frequency leads to stronger contractions.
    • Asynchronous Recruitment: Different motor units activate at different times to maintain sustained force without fatigue.

    Heart Anatomy and Function

    • Pathway of Blood:
      • Blood enters the right atrium via the superior vena cava.
      • Flows through the tricuspid valve to the right ventricle.
      • Exits through the pulmonary valve into the pulmonary trunk and lungs.
      • Returns via pulmonary veins to the left atrium.
      • Moves through the bicuspid (mitral) valve into the left ventricle.
      • Finally, exits through the aortic valve into the aorta.
    • ECG Waves:
      • P-Wave: Atrial depolarization initiating contraction.
      • QRS Complex: Ventricular depolarization, leading to ventricular contraction.
      • T-Wave: Ventricular repolarization, allowing for recovery.
    • AV and Aortic Valve Function: AV valves open and close based on pressure differences; increased aortic pressure impacts afterload and stroke volume.

    Breathing Mechanism

    • Inhalation:
      • Active process involving diaphragm, sternocleidomastoid, and intercostal muscles.
      • Volume increases, pressure decreases in the thoracic cavity.
    • Exhalation:
      • Can be passive or active; muscles include internal intercostals and abdominal muscles.
      • Volume decreases, pressure increases.
    • Pathway of Changes: Changes in pleural and lung spaces drive airflow during breathing.

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